UDIM / MultiTile map deficiencies and missing functionality

[senorpablo]

I'm trying to get UDIM going as part of our pipeline, which includes Max 2020. I'm running into numerous issues on the Max side at every step:

1. Getting UDIM maps to load:

• The 2021 Max documentation for MultiTile has no information as to what the file pattern options are expecting: 
  • https://knowledge.autodesk.com/support/3ds-max/learn-explore/caas/CloudHelp/cloudhelp/2021/ENU/3DSMa...
• When the wrong format is chosen, the error dialog box gives no hint as to what the correct pattern is, saying only: "Invalid file pattern format." This would be an intuitive place to let the user know what the format is.
• The Pixar specification suggests the UDIM naming convention is: Map.1001.tga. Unreal Engine also uses this naming convention. Why not support that?
• For the UDIM file pattern format option in Max, I've had to exhaust nearly every conceivable combination in a trial and error process before determining that Max wants Map-1001.tga. This seems to be a convention that only Autodesk products use.

2. Unwrap UVW - no snapping supported:

• None of the snapping functionality works with the MultiTile map type. The buttons are all there and can be enabled, but snapping doesn't work.
• Our pipeline requires perfectly precise pixel snapping so snaps not working with MultiTile is an issue.

3. Unwrap UVW texture preview size limited to 2048:

• MultiTile textures do not preview at their native resolution, unlike standard bitmaps which display correctly at resolutions of at least 4096 and possibly larger.
• Custom preview size option found under Options->Preferences, Display Preferences, Render Width/Height are limited to 2048 so that doesn't help matters. In 2020, why is this capped to a resolution that was state of the art fifteen years ago in 2005? 
• We're using 4096 x 4096 textures so this is another critical problem. 

The missing functionality enumerated in issues 2 and 3 make MultiTile unusable for us. All of the potential work arounds for these issues that I can think of will take considerable time to implement and be prone to user error. The MultiTile implementation in 2020 is pretty disappointing. 

[CiroCardoso3v]

What do you use to render? OSL Bitmap Lookup supports UDIM straight from Substance Painter for example. Using the map.1001 naming convention.

[senorpablo]

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@CiroCardoso3v wrote:

What do you use to render? OSL Bitmap Lookup supports UDIM straight from Substance Painter for example. Using the map.1001 naming convention.

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Thanks for the suggestion. Unfortunately, this isn't a rendering issue, it's an asset production issue. We need to create assets that are compatible with UDIM for export and use in Unreal. Pixel snapping and the ability to view 4096 textures in Unwrap UVW is a requirement for creating the assets in Max. 

[CiroCardoso3v]

Ok. I gave the suggestion of OSL Bitmap Lookup, because is render agnostic and you can see the textures in the viewport. Perhaps that could help.

[senorpablo]

As a follow up to this post, some additional discoveries:

• The viewport resolution for the MultiTile texture is controlled by the viewport configuration setting for 'Baked Procedural Maps' rather than the more obvious 'Texture Maps.' Odd choice.
• While the MultiTile UDIM textures display in the Unwrap UVW modifier and render correctly, textures beyond 1 do not display in the viewport. This is a fundamental shortcoming. 

I tried various OSL maps, but they neither display correctly in the viewport, Unwrap UVW modifier, nor render correctly in scanline. Snapping in the Unwrap UVW modifier are also not supported with OSL.